The Par 38 is probably the simplest fixture there is. It has an A Lamp Socket, meaning a traditional screw in base socket that houses your American regular light bulb. The Altman Unit can lamp up to 300 watts and the Leviton Units can lamp up to 120 watts. They can take a regular light bulb but are more effective with a flood light style lamp as the reflector system built into the lamp pushes light forward as opposed to a regular light bulb that disperses the light in all directions. If using a flood lamp this is a par can that will give a circle of light as opposed to an oval of light. The theatrical par 38 fixture does have accessory clips on the front of the unit for gel frames and light weight snoots. The Altman fixture can handle a barn door. The general uses for a par 38 is a short throw color wash, up light or even “area” light for small stages. The actual fixture housing on a par 38 is merely a housing for the lamp. It is the lamp you choose that will determine your intensity and size.